Linear for protection of adhesives

ABSTRACT

Release liners and methods protect one or more adhesives, wherein the release liners and/or methods comprise at least one abhesive release layer and at least one layer of a getter material capable of sorbing at least one permeable substance, wherein the getter material is at least one substance selected from the group consisting of lithium, beryllium, boron, sodium, magnesium, potassium, calcium, manganese, iron, nickel, zinc, gallium, germanium, cadmium, indium, caesium, barium, boron oxide, calcium oxide, chromium oxide, manganese oxide, iron oxide, copper oxide, silver oxide, indium oxide, barium oxide, lead oxide and mixtures of two or more of the above substances.

This is a continuation patent application of U.S. Ser. No. 13/719,277which was filed on Dec. 19, 2012, which claims foreign priority benefitunder 35 U.S.C. § 119 of German Application No. DE 10 2011 089 566.3filed Dec. 22, 2011.

The present invention relates to the technical field of the liners forthe protection of adhesives that are used, for example, for adhesivetapes. A new such liner is proposed which features an enhancedprotective function with respect more particularly to permeablesubstances. The invention further relates to an adhesive at leastpartially covered with the liner, and also to a method for theprotection of an adhesive and to the use of getter materials in liners.

Optoelectronic arrangements are being used with ever-increasingfrequency in commercial products or are close to market introduction.Such arrangements comprise organic or inorganic electronic structures,examples being organic, organometallic or polymeric semiconductors orelse combinations of these. Depending on the desired application, theproducts in question are rigid or flexible in form, there being anincreasing demand for flexible arrangements. Arrangements of this kindare frequently produced by printing techniques such as relief, gravure,screen or planographic printing or else by what is known as non-impactprinting such as, for instance, thermal transfer printing, inkjetprinting or digital printing. In many cases, however, vacuum techniquesare used as well, such as chemical vapour deposition (CVD), physicalvapour deposition (PVD), plasma-enhanced chemical or physical depositiontechniques (PECVD), sputtering, (plasma) etching or vapour coating.Patterning generally takes place through masks.

Examples of optoelectronic applications that are already availablecommercially or are of interest in terms of their market potentialinclude electrophoretic or electrochromic constructions or displays,organic or polymeric light-emitting diodes (OLEDs or PLEDs) in readoutand display devices or as illumination, and also electroluminescentlamps, light-emitting electrochemical cells (LEECs), organic solar cellssuch as dye or polymer solar cells, inorganic solar cells, moreparticularly thin-film solar cells, based for example on silicon,germanium, copper, indium and selenium, organic field-effecttransistors, organic switching elements, organic optical amplifiers,organic laser diodes, organic or inorganic sensors or else organic- orinorganic-based RFID transponders.

A perceived technical challenge for the realization of sufficientlifetime and function of optoelectronic arrangements in the area oforganic and inorganic optoelectronics, especially of organicoptoelectronics, is the protection of the components they containagainst permeates. Permeates are generally considered to be gaseous orliquid substances which penetrate a solid body and may pervade it ormigrate through it. Accordingly, numerous organic or inorganic compoundsof low molecular mass may be permeates, with water vapour and oxygenbeing of particular significance in the context presently described.

A multiplicity of optoelectronic arrangements—especially where organicmaterials are used—are sensitive both to water vapour and to oxygen.During the lifetime of the electronic arrangements, therefore,protection is necessary through encapsulation, since otherwise there isa dropoff in performance over the application period. Otherwise, forexample, oxidation of the constituents of light-emitting arrangementssuch as electroluminescent lamps (EL lamps) or organic light-emittingdiodes (OLEDs) may drastically reduce the luminosity, the contrast inthe case of electrophoretic displays (EP displays) or the efficiency inthe case of solar cells, within a short time.

Within the field of inorganic and more particularly organicoptoelectronics, therefore, there is a high demand for flexible adhesivebonding solutions which represent a barrier to permeates such as oxygenand/or water vapour. A number of approaches to such adhesive bondingsolutions can already be found in the prior art.

Accordingly, with relative frequency, liquid adhesives and adhesivebonding agents based on epoxides are used as barrier adhesives, as aredescribed in WO 98/21287 A1, U.S. Pat. Nos. 4,051,195 A and 4,552,604 A,for example. Their principal field of use is in marginal bonds in rigidarrangements, but also moderately flexible arrangements. Curing takesplace thermally or by means of UV radiation.

The use of these liquid adhesives is accompanied, however, by a seriesof unwanted effects as well. For instance, low molecular massconstituents (VOCs—volatile organic compounds) may damage the sensitiveelectronic structures of the arrangement and hinder production. Theadhesive, furthermore, has to be applied, in a costly and inconvenientprocedure, to each individual constituent of the arrangement. Theacquisition of expensive dispensers and fixing devices is necessary inorder to ensure precise positioning. The nature of the application hasthe effect, moreover, of preventing a rapid, continuous operation. Inthe laminating step that is subsequently necessary, the low viscositymay hinder the attainment of a defined film thickness and bond width.

An alternative is to use pressure-sensitive adhesives or hotmeltadhesives to seal optoelectronic constructions. Among thepressure-sensitive adhesives (PSAs) preference is given to using thosewhich after bonding are crosslinkable by introduction of energy (forexample actinic radiation or heat). Adhesives of these kinds aredescribed in US 2006/0100299 A1 and WO 2007/087281 A1 for example. Theiradvantage lies in particular in the fact that the barrier effect of theadhesives can be enhanced by crosslinking.

Also known in the prior art is the use of hotmelt (HM) adhesives. Usedhere in many cases are copolymers of ethylene, as for exampleethylene-ethyl acetate (EEA), ethylene-acrylic acid copolymer (EAA),ethylene-butyl acrylate (EBA) or ethylene-methyl acrylate (EMA).Crosslinking ethylene-vinyl acetate (EVA) copolymers are in general usedmore particularly for solar cell modules based on silicon wafers.Crosslinking takes place during the sealing operation under pressure andat temperatures of above around 120° C. For many optoelectronicconstructions based on organic semiconductors or produced in thin-filmprocesses, this operation is deleterious, as a result of the hightemperatures and the mechanical load imposed by the pressure.

Hotmelt adhesives based on block copolymers or functionalized polymersare described in WO 2008/036707 A2, WO 2003/002684 A1, JP 2005-298703 Aand US 2004/0216778 A1 for example. An advantage of these adhesives isthat the adhesives themselves do not introduce any substance—or onlyvery little substance—into the construction to be encapsulated thatitself harms the construction, whereas this problem is relevantparticularly in the case of reactive liquid adhesive systems, moreparticularly those based on acrylate or on epoxy resin. In view of thehigh number of reactive groups, these systems have a relatively highpolarity, and so, in particular, water is present therein. The amount isgenerally in the range of less than 100 ppm up to more than 1%. For thisreason among others, such liquid adhesives—as already mentionedabove—are used primarily as an edge sealant for the electronicarrangements, where they are not in direct contact with the activeelectronic materials.

Another possibility for countering the problem of entrained permeates isto include additionally an absorbing material—called a getter—within theencapsulation, this getter binding—by absorption or adsorption, forexample—water or other permeates that permeate through the adhesive ordiffuse out of it. An approach of this kind is described in EP1407818A1, US 2003/0057574 A1 and in US 2004-0169174 A1, among others.

Another measure is to equip the adhesive and/or the substrate and/or thecover of the electronic construction with such binding properties, as isdescribed in WO 2006/036393 A2, DE10 2009 036 970 A1 and DE 10 2009 036968 A1, for example.

It is possible, furthermore, to use raw materials with a particularlylow permeate content or to free the adhesive from permeating substancesduring production or prior to application, by means, for example, ofthermal drying, vacuum drying, freeze drying or the admixing of getters.Disadvantages of such methods are the long drying time and the possiblyhigh or low drying temperatures, which may harm the adhesive or initiatechemical reactions, such as crosslinking for example. Moreover, theoperation of admixing and subsequently removing the getters is costlyand inconvenient.

Where such adhesive-related measures are taken to reduce theintroduction of harmful permeating substances into the construction thatis to be protected, it is necessary to maintain the properties producedwith the minimum possible restriction, until the adhesive is used. Thus,for example, an adhesive which has been produced in a particularlyanhydrous procedure must be protected from water uptake from theenvironment. Moreover, any getter substances present in the adhesivemust be protected against premature saturation from the take-up ofpermeates from the environment.

This problem is generally solved by providing the adhesives withpackaging which is impervious to permeation or at least which inhibitspermeation. Liquid adhesives are generally dispensed into correspondingcontainers, made of metal, for example. Adhesive tapes are often weldedinto flexible pouches made from permeation-inhibiting material—forexample from polyethylene film or from a film laminate of aluminium andpolyester. The packaging materials themselves must be very largely freefrom permeates that might be released on the contents side.

In order to counter weaknesses in the imperviosity of the packaging orto ensure rapid binding of permeates included, a getter is oftenincluded in the packaging as well, in the form for example of a pouchfilled with silica gel or zeolite. This getter is generally not indirect contact with the contents. A particular disadvantage with thismethod is the increased cost and inconvenience of packaging.

A specific problem arises in the packaging of sheetlike adhesives, i.e.adhesive tapes or adhesive sheets: when they are stacked as shapes orwound to form a roll, gas—air, for example—is included, which is not inexchange with the rest of the gas space remaining in the packaging.Unwanted permeates present, for example water vapour, therefore do notreach the getter material located in the packaging, and may thereforemigrate into the adhesive. Furthermore, such adhesive tapes generallyinclude a temporary liner material, and also often a carrier material aswell. These materials may likewise comprise unwanted permeates, whichmay easily permeate into the adhesive in view in particular of the largearea of contact with said adhesive. Getter pouches or getter padsintroduced into the packaging may not reliably scavenge and bind thesepermeates. Freeing the liner materials and carrier materials entirelyfrom the unwanted permeates, by means of drying, for example, islaborious, costly and inconvenient.

EP 2 078 608 A1 discloses the use of liner materials which comprise aspecial permeation barrier. This approach, however, is not effectiveagainst permeates present in the liner or included between liner andadhesive.

There is therefore an ongoing need for liners which reliably protect asheetlike adhesive from the influence of permeates.

It is an object of the present invention, therefore, to provide a linerwhich protects an adhesive not only from permeates originating from theenvironment but also from permeates included in the course of winding orstacking and other processing steps. Accordingly, in the case of aproduct, such as an adhesive tape, which comprises a largelypermeate-free adhesive layer, this adhesive layer is to be kept largelyfree from permeates for the period of storage and of transport, with theadhesive layer preferably in fact being freed from remaining permeatesas well.

The achievement of this object derives from the fundamental concept ofthe present invention, namely providing a liner with getter materialscontained therein.

The invention therefore first provides a liner for the protection ofadhesives, which comprises at least one abhesive release layer and atleast one layer of a getter material capable of sorbing at least onepermeable substance, the getter material being selected from lithium,beryllium, boron, sodium, magnesium, silicon, potassium, calcium,manganese, iron, nickel, zinc, gallium, germanium, cadmium, indium,caesium, barium, boron oxide, calcium oxide, chromium oxide, manganeseoxide, iron oxide, copper oxide, silver oxide, indium oxide, bariumoxide, lead oxide, phosphorus oxide, sodium hydroxide, potassiumhydroxide, metal salts, metal hydrides, anhydrides of single andmultiple carboxylic acids, sodium dithionite, carbohydrazide,ascorbates, gallic acid, zeolites, carbon nanotubes, activated carbonand carbodiimides and also mixtures of two or more of the abovesubstances.

A liner of this kind advantageously prevents the penetration ofpermeates from the environment into the adhesive to be protected, and isalso capable of binding permeates present in the adhesive and permeatesincluded between liner and adhesive. The adhesive itself, or a productcomprising the adhesive, need therefore not be separately pretreated—bydrying, for example.

Adhesive tapes coated with adhesives on one or both sides are usuallywound up at the end of the production procedure into a roll in the formof an Archimedean spiral. In order to prevent the adhesives indouble-sided adhesive tapes from coming into contact with one another,or in order to prevent the adhesive sticking to the carrier in the caseof single-sided adhesive tapes, the adhesive tapes are lined beforewinding with a liner material (also called release material) which iswound up together with the adhesive tape. The skilled person knows ofsuch liner materials as simply liners or release liners. In addition tothe lining of single-sided or double-sided adhesive tapes, liners arealso used for lining pure adhesives (adhesive transfer tape) andadhesive-tape sections (for example label).

A liner, accordingly, is a covering material which has an antiadhesive(abhesive) surface and is applied, for the temporary protection of anadhesive, directly to the adhesive, and can generally be removed bysimple peeling immediately prior to application of the adhesive.

These release liners also ensure that the adhesive is not contaminatedprior to use. In addition, release liners can be tailored via the natureand composition of the release materials to allow the adhesive tape tobe unwound with the desired force (easy or difficult). In the case ofadhesive tapes coated with adhesive on both sides, moreover, the releaseliners ensure that the correct side of the adhesive is exposed firstduring unwinding.

A liner is not part of an adhesive tape, but merely an aid to itsproduction, storage or further processing. Furthermore, in contrast toan adhesive tape carrier, a liner is not firmly joined to a layer ofadhesive; instead, the assembly is only temporary and not permanent.

A liner of the invention contains at least one abhesive release layer.The term “abhesive” expresses in accordance with the invention the ideathat the release layer has a lower adhesion to the adhesive that is tobe covered than does the adhesive to the intended application substratein its use, and, where appropriate, to the carrier material belonging tothe adhesive.

The material of the abhesive release layer is preferably selected fromthe group encompassing silicones, fluorinated silicones, siliconecopolymers, waxes, carbamates, fluoropolymers and polyolefins ormixtures of two or more of the stated substances. With particularpreference the material of the abhesive release layer is selected fromsilicones and polyolefins.

The system forming the abhesive release layer is preferably formulatedin such a way that there is essentially no diffusion of abhesivesubstances into the adhesive. Analytically it may still be possible todetect substances from the abhesive coating, but these can be attributedto mechanical abrasion.

The abhesive release layer preferably has essentially no vapour pressureat room temperature.

The abhesive release layer preferably consists of a silicone system.Such silicone systems are preferably produced using crosslinkablesilicone systems. These include mixtures of crosslinking catalysts andso-called thermally curable, condensation-crosslinking oraddition-crosslinking polysiloxanes. As crosslinking catalysts forcondensation-crosslinking silicone systems, there are frequently tincompounds present in the composition, such as dibutyltin diacetate.

Silicone-based release agents on an addition-crosslinking basis can becured by hydrosilylation. These release agents typically comprise thefollowing constituents:

-   -   an alkenylated polydiorganosiloxane (more particularly, linear        polymers having terminal alkenyl groups),    -   a polyorganohydrogensiloxane crosslinking agent and    -   a hydrosilylation catalyst.

Established catalysts for addition-crosslinking silicone systems(hydrosilylation catalysts) include, for example, platinum or compoundsof platinum, such as the Karstedt catalyst (a Pt(0) complex compound)for example.

Thermally curing release coatings are therefore frequentlymulti-component systems, consisting typically of the followingcomponents:

-   -   a) a linear or branched dimethylpolysiloxane which consists of        around 80 to 200 dimethylpolysiloxane units and is stopped with        vinyldimethylsiloxy units at the chain ends. Typical        representatives are, for example, solvent-free,        addition-crosslinking silicone oils having terminal vinyl        groups, such as Dehesive® 921 or 610, both available        commercially from Wacker-Chemie GmbH;    -   b) a linear or branched crosslinker, typically composed of        methylhydrogensiloxy units and dimethylsiloxy units, with the        chain ends being satisfied either with trimethylsiloxy groups or        dimethylhydrogensiloxy groups. Typical representatives of this        class of product are, for example, hydrogenpolysiloxanes having        a high reactive Si—H content, such as the crosslinker V24, V90        or V06, which are available commercially from Wacker-Chemie        GmbH;    -   c) a silicone MQ resin, possessing as M unit not only the        trimethylsiloxy units typically used but also        vinyldimethylsiloxy units. Typical representatives of this group        are, for example, the release force regulators CRA® 17 or CRA®        42, available commercially from Wacker-Chemie GmbH;    -   d) a silicone-soluble platinum catalyst such as, for example, a        platinum-divinyltetramethyldisiloxane complex, which is commonly        dubbed Karstedt complex and is available commercially for        example under the name Katalysator OL from Wacker-Chemie GmbH.

It is also possible to use photoactive catalysts, known asphotoinitiators, in combination with UV-curable, cationicallycrosslinking siloxanes based on epoxide and/or vinyl ether, and/orUV-curable, free-radically crosslinking siloxanes such as, for instance,acrylate-modified siloxanes. The use of electron beam-curable siliconeacrylates is likewise possible. Such systems, depending on theirintended use, may also include further additions such as stabilizers orflow control assistants.

Silicone-containing systems may be acquired commercially from DowCorning, Wacker or Rohm&Haas, for example.

One example is Dehesive® 914, which comprises avinylpolydimethylsiloxane, Crosslinker V24, a methylhydrogenpolysiloxaneand Catalyst OI, a platinum catalyst in polydimethylsiloxane. Thissystem is available from Wacker-Chemie GmbH.

Also possible for use, for example, is the commercially availableaddition-crosslinking silicone release system Dehesive® 940A fromWacker-Chemie with an associated catalyst system, which is applied inthe non-crosslinked state and then subsequently crosslinked in theapplied state.

Among the stated silicones, the addition-crosslinking silicones have thegreatest economic importance. An undesirable feature of these systems,however, is their sensitivity to catalyst poisons, such as heavy metalcompounds, sulphur compounds and nitrogen compounds, for example (inthis regard, cf. “Chemische Technik, Prozesse and Produkte” by R.Dittmeyer et al., volume 5, 5th edition, Wiley-VCH, Weinheim, Germany,2005, section 6-5.3.2, page 1142). Generally it is the case thatelectron donors may be considered to be platinum poisons (A. Colas,Silicone Chemistry Overview, Technical Paper, Dow Corning). Accordingly,phosphorus compounds such as phosphines and phosphites are among thosecompounds considered to be platinum poisons. The presence of catalystpoisons means that the crosslinking reaction between the differentconstituents of a silicone release coating material takes place nolonger at all or only to a small extent. In the production ofantiadhesive silicone coatings, therefore, the presence of catalystpoisons, more particularly of platinum poisons, is strictly avoided. Thegetter material present in the liner of the invention is thereforepreferably not a platinum poison.

Particular embodiments of the silicone systems are polysiloxane blockcopolymers, with a urea block, for example, like those available fromWacker under the tradename “Geniomer”, or release systems comprisingfluorosilicones, which are used in particular with adhesive tapesfeaturing silicone adhesives.

Polyolefinic release layers may consist of thermoplastic, non-elastic orelastic materials. For example, such release layers may be based onpolyethylene. For this purpose it is possible to utilize polyethylenesin the entire realisable density range from approximately 0.86 g/cm³ to1 g/cm³. For certain applications, polyethylenes of lower density areappropriate with preference, since they frequently produce lower releaseforces.

Release layers having elastic properties may also consist ofolefin-containing elastomers. Examples include both random copolymersand block copolymers. Examples among the block copolymers includeethylene-propylene rubbers, butyl rubber, polyisobutylene, ethyleneblock copolymers and also partly and fully hydrogenated styrene-dieneblock copolymers such as, for example, styrene-ethylene/butylene andstyrene-ethylene/propylene block copolymers.

Suitable release layers can also be provided, furthermore, by acrylatecopolymers. Preferred embodiments of this variant are acrylate polymershaving a static glass transition temperature (mid-point Tg as determinedvia differential calorimetry) which is below room temperature. Thepolymers are typically crosslinked. Crosslinking may be chemical orphysical, of the kind realized in block copolymers, for example.

The at least one abhesive release layer of the liner of the inventionpreferably has a layer thickness of 0.5 μm to 300 μm. This rangeembraces not only thin coatings of the release layer material (forexample silicone) but also carrierless liners, which are producedcompletely from the release layer material (for example a sheet of asuitable polyolefin).

The abhesive release layer may be applied directly by means of a coatingbar from solution, emulsion or dispersion. The solvent, emulsifyingmedium or dispersing medium used, respectively, may in this case beevaporated subsequently in a commercial dryer. Solvent-free coating bymeans of a nozzle or roll coating unit is also suitable.

In accordance with the invention the abhesive layer may also be printed.Suitable for this purpose in accordance with the prior art are gravureand screen printing processes. It is preferred here to employ rotaryprinting processes. Furthermore, abhesive coatings may also be appliedby spraying. This may take place in a rotary spraying process,optionally also electrostatically.

The material of the abhesive release layer and the material of anycarrier layer optionally present need not take the form of homogeneousmaterials, but instead may also consist of mixtures of two or morematerials. Accordingly, for the purpose of optimizing the propertiesand/or processing, the materials may in each case have been blended withone or more additives such as resins, waxes, plasticizers, fillers,pigments, UV absorbers, light stabilizers, ageing inhibitors,crosslinking agents, crosslinking promoters, defoamers, degassingagents, wetting agents, dispersing assistants, rheological additives orelastomers.

In the simplest case, the liner of the invention consists only of theabhesive release layer and of a layer of a getter material capable ofsorbing at least one permeable substance (this material also beingidentified below as “getter material layer” or as “getter layer”). In afurther embodiment, the liner of the invention includes at least onecarrier layer. In this case the abhesive release layer may be applieddirectly to the carrier layer or to the getter material layer and may atleast partially cover said layer. The getter material layer maytherefore be disposed between carrier material and release layer and/oron the side which is opposite the release-layer-coated side of thecarrier material. Typically, an abhesive release layer is applied in theform of a continuous (uninterrupted) outermost layer at least on theadhesive-facing side of the carrier material.

Independently of the presence of a carrier layer, the liner of theinvention may also have an abhesive surface on both sides, at leastpartially, and this surface may be the same or different.

As carrier material of the liner it is possible to use papers,plastic-coated papers or sheets, with preference being given to sheets,more particularly to dimensionally stable polymeric films or metallicfoils. The at least one carrier layer therefore consists preferably ofpolyesters, more particularly of polyethylene terephthalate, for exampleof biaxially oriented polyethylene terephthalate, or of polyolefins,more particularly of polybutene, cycloolefin copolymer,polymethylpentene, polypropylene or polyethylene, for example ofmonoaxially oriented polypropylene, biaxially oriented polypropylene orbiaxially oriented polyethylene. Polyester films have the advantage ofpossessing good barrier properties, ensuring temperature stability, andcontributing enhanced mechanical stability. With very particularpreference, therefore, the at least one carrier layer of the liner ofthe invention consists of a polyester film, for example of biaxiallyoriented polyethylene terephthalate.

Papers or nonwoven webs are other suitable carrier materials.

In one preferred embodiment the liner of the invention comprises abarrier layer against one or more specific permeates, more particularlyagainst water vapour and oxygen. It is likewise preferred in accordancewith the invention for the liner to comprise at least one carrier layerand for this carrier layer to have a barrier function against one ormore specific permeates. A barrier function of this kind may consist oforganic or inorganic materials. Carrier materials with a barrierfunction are set out comprehensively in EP 2 078 608 A1.

With particular preference the liner of the invention comprises at leastone inorganic barrier layer. Suitable inorganic barrier layers includemetal nitrides or metal hydronitrides that are deposited particularlywell under reduced pressure (for example by means of evaporation, CVD,PVD, PECVD or ALD (Atomic Layer Deposition)) or under atmosphericpressure (for example by means of atmospheric plasma, reactive coronadischarge or flame pyrolysis), examples being nitrides of silicon, ofboron, of aluminium, of zirconium, of hafnium or of tellurium; and alsooxides of silicon, of boron, of aluminium, of zirconium, of hafnium andof tellurium; and also indium tin oxide (ITO). Likewise suitable arelayers of the aforementioned variants that are doped with furtherelements.

With particular preference the liner of the invention comprises at leastone carrier layer and at least one barrier layer against one or morespecific permeates, the barrier layer and the carrier layer taking theform of layers which follow one another directly. A particularlysuitable method for applying an inorganic barrier layer is high-powerimpulse magnetron sputtering or atomic layer deposition by means ofwhich it is possible to realize layers which are particularly imperviousto permeation, while imposing a low temperature load on the carrierlayer. Preference is given to a permeation barrier, of the carrier layerwith barrier function or of the assembly of carrier layer and barrierlayer, against water vapour (WVTR) of <1 g/(m²*d) and/or against oxygen(OTR) of <1 cm³/(m²*d*bar), the value being based on the respectivecarrier layer thickness used in the liner, in other words notstandardized to a specific thickness. The WVTR is measured at 38° C. and90% relative atmospheric humidity in accordance with ASTM F-1249, andthe OTR is measured at 23° C. and 50% relative atmospheric humidity inaccordance with DIN 53380-Part 3.

The liner of the invention further comprises at least one layer of agetter material capable of sorbing at least one permeable substance.

“Sorbing” refers to “sorption”, this being the process of selectivetake-up of one substance or of a plurality of substances by anothersubstance—in accordance with the invention, by the getter material. Thesorbing of the permeable substance(s) by the getter material may takeplace, for example, by absorption or adsorption and adsorption may occurboth in the form of chemisorption and of physisorption.

A “permeable substance” is a substance which as a gaseous or liquidsubstance, or possibly even as a solid substance, is able to penetrateinto the adhesive to be protected, and subsequently to saturate it.Substances of this kind are referred to below—as has already been thecase a number of times in the present text—as “permeates”. The permeatesmay originate from the adhesive itself or from the environment, as forexample from the carrier material of an adhesive tape coated with theadhesive. From the adhesive or from the adhesive tape itself come,frequently, low molecular mass organic compounds such as solventresidues, residual monomers, oils, resin components, plasticizers andwater. The environment is often a source of water, volatile organiccompounds (VOCs), low molecular mass hydrocarbons and oxygen. Substancesconsidered to be “permeable substances” include more particularly thefollowing:

acetonitrile, 1-butanol, chlorobenzene, chloroform (trichloromethane),cyclohexane, diethyl ether, 1,4-dioxane, glacial acetic acid (aceticacid), acetic anhydride, acetic acid ethyl ester (ethyl acetate, ethylethanoate), acetic acid n-butyl ester (n-butyl acetate), acetic acidtert-butyl ester (tert-butyl acetate), ethanol, methanol, n-hexane,n-heptane, 3-hexanone, 2-propanol (isopropanol), 3-methyl-1-butanol(isoamyl alcohol), methylene chloride (dichloromethane), methyl ethylketone (butanone), methyl isobutyl ketone, nitromethane (nitrocarbol),n-pentane, 2-pentanone, 3-pentanone, petroleum ether (light benzine),benzine, propanol, pyridine (azine), tert-butyl methyl ether,tetrachloroethene (perchloroethene), tetrahydrofuran, toluene,trichloroethane, triethylamine, xylene, oxygen, methane, ethane,propane, propene, butane, butene, carbon dioxide, ozone, sulphurdioxide, water.

A “getter material” is a material which—in the sense of the processdefined above as “sorption”—is able selectively to take up at least onepermeable substance. The getter material could therefore also bereferred to as a “sorbent” or “sorption agent”. The getter material ispreferably capable at least of the sorption of water.

The getter material takes the form preferably of a coherent, continuousand uninterrupted layer. Alternatively it may also be an interruptedlayer or else have holes. In accordance with the invention it ispossible to apply a full-area or interrupted layer of getter material inpowder form to a carrier material and to bind it to the subsequentlyapplied release layer on the carrier material by means for example of athermal and/or mechanical operation such as hot rolling, for example. Aninterrupted layer has the advantage that permitted permeates are able topass through the layer more easily, but permeates which are to be boundare captured. Moreover, an interrupted layer consisting of particles,for example, has a higher surface area than a full-area, smooth layer,and so the sorption capacity of the getter material is manifested moreeffectively.

The thickness of the getter material layer is dependent in particular onthe desired take-up capacity for the particular permeate. A lower limitcan be regarded as being constituted by the minimum thickness of acontinuous layer of a getter material with high take-up capacity, forexample a calcium layer, and may be estimated at about 20 nm. Consideredas an upper limit is the thickness of a foil consisting of metallicgetter material, as for example of a barium-zinc alloy, which in termsof its stiffness still allows an adhesive tape to be wound up. A layerthickness of this kind may be put at around 100 μm.

The getter material layer is preferably made of the pure gettermaterial. It is, for example, a getter material layer applied by vapourdeposition or sputtering. In a further embodiment there is at least oneadditional material present in dispersion in the getter layer. Thisfurther material is, for example, a gas, and so the getter layer withparticular advantage takes the form of a foam, more particularly anopen-celled foam. This has the advantage of a particularly high activesurface area for the getter layer. Methods for producing metal foams areknown from DE 10 2009 020 004 A1 for example. Materials in solid orliquid state as well may be present in dispersion in the getter materiallayer. These may be, for example, materials which bind a getter materialwhich undergoes liquefaction on take-up of permeate, such as lithiumchloride for example, or which bind evolving gases, as for examplehydrogen in the case of the reaction of barium with water. Pore formersas well, which are removed again after the getter material layer hasformed, may constitute the material in dispersion in the getter layer.These may be, for example, organic materials which are initiallyincorporated during electrochemical deposition of a getter materiallayer, but in a subsequent step are leached out again, and so leavebehind a porous getter material structure.

A getter material present in dispersed form (as dispersed phase) in alayer of the liner is not a “layer of a getter material capable ofsorbing at least one permeable substance” in the sense of the invention.A “layer of a getter material capable of sorbing at least one permeablesubstance” in accordance with the invention is present only when thelayer is formed substantially by the getter material itself, for exampleas exclusive material of the layer or as continuous phase of adispersion. A continuous phase of a dispersion is also considered in thesense of the invention to be represented by percolated particles. By“percolated particles” are meant particles which are in interaction withone another in such a way as to form coherent regions or clusters. Sincethe presence of a percolation is not immediately detectable, a weightfraction of the getter material of 50% within a dispersion is definedalternatively as a percolation threshold.

In accordance with the invention the getter material is selected fromlithium, beryllium, boron, sodium, magnesium, silicon, potassium,calcium, manganese, iron, nickel, zinc, gallium, germanium, cadmium,indium, caesium, barium, boron oxide, calcium oxide, chromium oxide,manganese oxide, iron oxide, copper oxide, silver oxide, indium oxide,barium oxide, lead oxide, phosphorus oxide, sodium hydroxide, potassiumhydroxide, metal salts, metal hydrides, anhydrides of single andmultiple carboxylic acids, carbohydrazide, ascorbates, gallic acid,zeolites, carbon nanotubes, activated carbon and carbodiimides and alsomixtures of two or more of the above substances.

The metal salts are preferably selected from cobalt chloride, calciumchloride, calcium bromide, lithium chloride, lithium bromide, zincchloride, zinc bromide, calcium sulphate, copper sulphate, sodiumdithionite, sodium carbonate, sodium sulphate, potassium carbonate,magnesium carbonate, magnesium chloride, potassium sulphite, magnesiumperchlorate, barium perchlorate, aluminium sulphate, barium sulphate,magnesium sulphate, lithium sulphate and cobalt sulphate.

The metal hydrides are preferably selected from calcium hydride, sodiumhydride and lithium aluminium hydride.

Anhydrides of single and multiple carboxylic acids are preferablyselected from acetic anhydride, propionic anhydride, butyric anhydrideand methyltetrahydrophthalic anhydride.

In accordance with their function the getter materials are usedpreferably as materials free from permeates, for example in anhydrousform. It is also possible in accordance with the invention, however, touse materials that are already partly complexed with permeates, such asCaSO₄*½H₂O (calcium sulphate hemihydrate), for example.

“Carbodiimides” are compounds of the general formula R¹—N═C═N—R², whereR¹ and R² are organic radicals, more particularly alkyl radicals or arylradicals, which may be identical or different.

Preferably the getter material is selected from magnesium, calcium,manganese, iron, nickel, zinc, barium, barium oxide, boron trioxide,calcium chloride, calcium oxide, calcium sulphate, copper sulphate,lithium chloride, lithium bromide, magnesium chloride, magnesiumperchlorate, magnesium sulphate, phosphorus oxide, potassium carbonate,potassium hydroxide, sodium, sodium hydroxide, sodium sulphate, zincchloride, carbodiimides and zeolites and also mixtures of two or more ofthe above substances. These materials have a high sorption capacity forat least one of the abovementioned permeates and more particularly forwater.

With particular preference the getter material is selected frommagnesium, calcium, iron, barium, calcium oxide, chromium oxide,manganese oxide, iron oxide, copper oxide, silver oxide and barium oxideand also mixtures of two or more of the above substances. These gettermaterials offer the advantage that they can be deposited easily in layerform, for example by vacuum coating methods, to the relevant layer ofthe liner, and exhibit a high sorption capacity.

In a further preferred embodiment of the liner of the invention, thegetter material is selected from calcium oxide, calcium sulphate,calcium chloride, sodium sulphate, potassium carbonate, copper sulphate,magnesium perchlorate, magnesium sulphate and zeolites and also mixturesof two or more of the above substances. The feature of these materialsis that they are regenerable getter materials. By these are meantsubstances which are able to release absorbed permeates, for examplewater, again under defined conditions and thereby to enter a state whichenables them to take up permeate again. This makes possible a method inwhich the getter-containing liner, before being contacted with theadhesive, is largely freed—by drying, for example—from any permeatestaken up prior to that point in time. As a result of this,advantageously, the full getter capacity is available when the liner isused.

With very particular preference the getter material is selected frommagnesium, calcium, iron, barium, calcium oxide, calcium sulphate,calcium chloride and zeolites and also mixtures of two or more of theabove substances. These materials have particularly high capacities forthe uptake of water and further permeates, are very largely regenerable,and can be integrated outstandingly in layer form into the liner, forexample by coating onto a carrier layer or onto the abhesive releaselayer.

In the context of a particular embodiment of the liner of the invention,the getter material is selected from calcium, iron, barium, lithiumchloride, cobalt chloride and calcium oxide and also mixtures of two ormore of the above substances. These substances, via a change in theiroptical properties, allow conclusions to be drawn about the permeatecontent of the adhesive, by reacting to increasing water uptake, forexample, by a change from white (calcium oxide) or a metallically opaqueappearance (calcium, barium) to a transparent appearance or, in the caseof iron, to a brownish discoloration. Therefore, for as long as freegetter capacity is still evident from the optical appearance of theliner, this may be taken as an indication that up to that point nopermeate, or little permeate at most, has diffused into the adhesivethat is to be protected.

In a further preferred embodiment, the getter material binds thepermeate by chemisorption. Owing to the generally relatively highactivation energy, this process is slower than physisorption. One knownexample here is calcium oxide, which is converted by the water permeateinto calcium hydroxide. As a result of slower reaction, the possibilityis provided of handling the getter material for a short time in ambientatmosphere without already losing a substantial part of the uptakecapacity.

Preferred, moreover, is a getter material which possesses a highactivity even at low permeate concentration. For water as the permeate,accordingly, it is preferred to use those getter materials over whosesaturated aqueous solution a relative atmospheric humidity of less than20% is developed at 20° C. and an atmospheric pressure of 1013 mbar.From the standpoint of activity at low permeate concentration, thegetter material is preferably selected from the group encompassingsodium hydroxide, potassium hydroxide, lithium bromide, zinc bromide,lithium chloride, calcium bromide, lithium iodide and calcium acetate.

In a further preferred embodiment, the material of the abhesive releaselayer has a permeate permeability more particularly for water vapour ofat least 100 g/(m²*d), more preferably of at least 500 g/(m²*d), in eachcase based on a layer thickness of 50 μm. The permeability or permeationbarrier against water vapour (WVTR) is measured at 38° C. and 90%relative atmospheric humidity according to the ASTM F-1249; thepermeation barrier against oxygen is measured at 23° C. and 50% relativeatmospheric humidity in accordance with DIN 53380-Part 3. The statedpermeate permeability of the release layer material is advantageous inthat the permeate reaches the getter material layer particularly quicklyand effectively, especially from the adhesive. It is thereforeparticularly preferred to use a silicone-based or acrylate-based releaselayer.

The total amount of getter material in the liner of the invention may befrom 0.5% to 95% by weight, based on the total weight of all the layersof the liner. The amount depends substantially on the desired uptakecapacity for the permeate or permeates in question.

If, for example, only a low uptake capacity is required, it may besufficient to use a getter material having a low uptake capacity in alow layer thickness. In one preferred embodiment, therefore, the linercomprises 0.5% to 5% by weight of getter material, based on the totalweight of the liner. In this case the thickness and the area of thematrix containing drying agent may be situated advantageously at therespective lower limits.

In the case of a very high required uptake capacity on the part of theliner, however, it is necessary to use a getter material layer having ahigh thickness, and the getter material as well ought to possess a highuptake capacity. However, a getter material with a low uptake capacitycan also be used if advisable from the standpoint of cost orcompatibility. In the context of a further preferred embodiment of theliner of the invention, therefore, the liner comprises 60% to 95% byweight of getter material, based on the total weight of all the layersof the liner.

A getter material with a high uptake capacity (maximum acquirablepermeate weight >25% of the getter weight) is preferred, since by thismeans the amount of getter can be minimized. The uptake capacity isdetermined in this case after storage of the getter material for 100hours at 23° C. and 50% relative atmospheric humidity for water vapouras the permeate, or at 23° C. in a saturated atmosphere in the case ofother gaseous permeates. The permeate content of the getter afterstorage can be determined by gravimetry. From the standpoint of uptakecapacity, the getter material is preferably selected from the groupencompassing copper sulphate, calcium oxide and calcium chloride.

In one preferred embodiment the liner of the invention consists of acarrier layer, an abhesive release layer and a layer of a gettermaterial capable of sorbing at least one permeable substance. In thiscase, therefore, the liner contains exclusively these three layers. Thisis advantageous because such a liner is more flexible than a multilayerliner and the anchoring between the layers is easier to achieve thanwith a multilayer liner. Furthermore, a liner of this kind can beproduced using less material. Relative to a liner containing only onerelease layer, the embodiment with an additional carrier layer has theadvantage that the release function and the mechanical stabilizationfunction are present in decoupled form, in two layers, and hence thatparticularly suitable materials can be selected for each function.

In further preferred embodiments, the liner of the invention comprises acarrier layer, an abhesive release layer, a layer of a getter materialcapable of sorbing at least one permeable substance, and further layers.These further layers may be, for example, primer layers, enhancing theinterlaminar adhesion between other layers; optically active layers suchas printed layers or radiation filters, for example; or further releaselayers.

The liner of the invention is preferably transparent—that is, thetransmittance measured in accordance with ASTM D1003-00 (procedure A) isgreater than 50%, preferably greater than 75%. With a transparent linerthe adhesive tape can be positioned more easily in the application.

With particular preference the liner of the invention is opaque to UVlight—that is, the transmittance in a wavelength range from 200 to 400nm, measured in accordance with ASTM D1003-00 (procedure B), is lessthan 25%, preferably less than 10%. With a UV-opaque liner, the adhesivecan be protected from alterations (for example chemical reactions,ageing, crosslinking) as a result of the influence of UV light.

The present invention further provides an adhesive which is covered onat least one side and at least partially with a liner of the invention.The adhesive is preferably a pressure-sensitive adhesive or anactivatable adhesive and more particularly an activatablepressure-sensitive adhesive.

Pressure-sensitive adhesives (PSAs) are adhesives whose set film in thedry state at room temperature remains permanently tacky and adhesive.Even with relatively weak applied pressure, PSAs permit a durable bondto be made to the substrate, and after use can be detached from thesubstrate again with substantially no residue. The bondability of theadhesives is based on their adhesive properties, and theirredetachability on their cohesive properties.

In accordance with the invention it is possible to use all PSAs known tothe skilled person, thus including, for example, those based onacrylates and/or methacrylates, polyurethanes, natural rubbers,synthetic rubbers; styrene block copolymer compositions with anelastomer block composed of unsaturated or hydrogenated polydiene blockssuch as, for example, polybutadiene, polyisoprene, and copolymers ofboth and also further elastomer blocks familiar to the skilled person;polyolefins, fluoropolymers and/or silicones.

Where acrylate-based PSAs are referred to in the context of thisspecification, the term encompasses, without explicit reference, PSAsbased on methacrylates and those based on acrylates and methacrylates,unless expressly described otherwise. Likewise suitable for use in thesense of the invention are combinations and mixtures of two or more basepolymers and also adhesives additized with tackifier resins, fillers,ageing inhibitors and crosslinkers, the recitation of the additivesbeing only by way of example and being non-limiting in itsinterpretation.

Preference is given to PSAs based on styrene block copolymers,polybutylenes, polyolefins or fluoropolymers, since these adhesives arenotable for a high permeation barrier against water vapour and also fora low water content.

Activatable adhesives are considered to be those adhesive systems wherebonding is accomplished as a result of an input of energy, by actinicradiation or heat, for example.

Heat-activatedly bonding adhesives can be classed in principle in twocategories: thermoplastic heat-activatedly bonding adhesives (hotmeltadhesives) and reactive heat-activatedly bonding adhesives (reactiveadhesives). Likewise encompassed are those adhesives which can beassigned to both categories, namely reactive thermoplasticheat-activatedly bonding adhesives (reactive hotmelt adhesives).

Thermoplastic adhesives are based on polymers which on heating undergoreversible softening and solidify again during cooling. Thermoplasticadhesives which have emerged as being advantageous are especially thosebased on polyolefins and copolymers of polyolefins and also on theiracid-modified derivatives, on ionomers, on thermoplastic polyurethanes,on polyamides and also polyesters and copolymers thereof, and also onblock copolymers such as styrene block copolymers.

In contrast, reactive heat-activatedly bonding adhesives comprisereactive components. The latter constituents are also identified as“reactive resins”, in which heating initiates a crosslinking procedurewhich after the end of the crosslinking reaction ensures a durable,stable bond. Such adhesives preferably also comprise elastic components,for example synthetic nitrile rubbers or styrene block copolymers. Suchelastic components give the heat-activatedly bonding adhesiveparticularly high dimensional stability even under pressure, on accountof their high flow viscosity.

Radiation-activated adhesives are likewise based on reactive components.The latter constituents may comprise, for example, polymers or reactiveresins in which the irradiation initiates a crosslinking process whichafter the end of the crosslinking reaction ensures a durable, stablebond. Such adhesives preferably also comprise elastic components, suchas those recited above.

It is preferred to use activatable adhesives based on epoxides, oxetanes(meth)acrylates or modified styrene block copolymers.

The adhesive before being contacted with the liner of the inventionpreferably has a permeate content of less than 1000 ppm, more preferablyof less than 100 ppm. The ppm figure here refers to the relation betweenthe total weight of permeate present and the analyzed weight ofadhesive. The permeate content may be determined by means of headspacegas chromatography in accordance with VDA 277 or in the case of water byDIN EN ISO 62 (gravimetric technique, method 4) or DIN 53715(Karl-Fischer titration) after storage of the test specimen for 24 hoursat 23° C. and 50% relative atmospheric humidity. In the case of thepermeate contents of the adhesive that are described here, the capacityof the getter materials in the liner is not so greatly taxed bypermeates diffusing out of the adhesive, but the liner is able better tofulfil its function as a cover which protects against permeates from theenvironment.

The adhesive preferably has a low permeation rate for the permeate to beimmobilized. In the case of water vapour as the permeate, the watervapour permeation rate (WVTR) is preferably less than 50 g/m² day, morepreferably less than 20 g/m² day, based on an adhesive thickness of 50μm. The WVTR here is measured at 38° C. and 90% relative atmospherichumidity in accordance with ASTM F-1249, the oxygen permeation rate(OTR) is measured at 23° C. and 50% relative atmospheric humidity inaccordance with DIN 53380-Part 3.

As a result of the low permeation rate on the part of the adhesive, lesspermeate diffuses from the environment through the adhesive and into thegetter material-containing liner, which is able therefore to fulfil itsfunction for longer or can be furnished with a smaller amount of gettermaterial, thus reducing the materials usage and saving on costs.

The adhesive of the invention preferably takes the form of an adhesivetape. The adhesive tape thus comprises at least one layer of a PSA or ofan activatable adhesive or more particularly of an activatable PSA. Theadhesive tape may also comprise further layers, for example one or morefurther layers of adhesive, or a carrier material.

The adhesive tape preferably comprises only one layer of an adhesive(adhesive transfer tape), since this keeps the construction simple andallows the number of possible permeates that need be taken into accountto be kept small, as a result of the relatively low diversity ofmaterials. Furthermore, there is no carrier material to hinder thediffusion of permeates from the adhesive tape to the getter-containingliner, allowing the adhesive tape to be freed from permeates in aparticularly efficient way.

The thickness of the adhesive tape may span all customary thicknesses,in other words, approximately, from 3 μm up to 3000 μm. A thickness ofbetween 25 and 100 μm is preferred, since within this range, bondstrength and handling properties are particularly positive. A furtherpreferred range is a thickness of 3 to 25 μm, since in this range theamount of substances permeating through the bondline can be minimizedsolely by the small cross-sectional area of the bondline in anencapsulation application. It has surprisingly emerged, moreover, thatsuch low adhesive tape thicknesses can be freed effectively frompermeates through the getter-filled liner.

Particularly preferred are adhesive transfer tapes, since in that casethere is no carrier material to hinder the diffusion of permeates fromthe adhesive tape to the getter-containing liner and hence the adhesivetape can be freed from permeates in a particularly efficient way.

The present invention further provides a method for the protection of anadhesive from permeates, this method comprising the at leastsingle-sided and at least partial covering of the adhesive with a linerof the invention.

To produce an assembly composed for example of an adhesive tape and aliner of the invention, the carrier of the adhesive tape, or the liner,is coated or printed on one side with the preferred PSA of the adhesivetape, from solution or dispersion or in 100% form (as a melt, forexample), or the assembly is produced by coextrusion. An alternativeoption is to form the assembly by transfer of a layer of adhesive or ofa liner by lamination. The layer or layers of adhesive may becrosslinked by heat or high-energy radiation.

This operation preferably takes place in an environment in which thespecific permeate is present only in a low concentration or almost notall. An example that may be given is a relative atmospheric humidity ofless than 30%, preferably of less than 15%.

To optimize the properties it is possible for the self-adhesivecomposition employed to be blended with one or more additives such astackifiers (resins), plasticizers, fillers, pigments, UV absorbers,light stabilizers, ageing inhibitors, crosslinking agents, crosslinkingpromoters or elastomers.

The amount of the layer of adhesive is preferably 1 to 5000 g/m²,preferably 10 to 100 g/m², where “amount” means the amount after anyremoval of water or solvent that may be carried out.

The present invention additionally provides for the use of gettermaterial capable of sorbing at least one permeable substance for thefurnishing of liners for the protection of adhesives.

Additionally provided for the present invention is the use of a liner ofthe invention for the at least single-sided and at least partialcovering of adhesive tape in methods for the encapsulation ofoptoelectronic components and/or of an aerobically curing adhesiveand/or of a moisture-curing adhesive.

The present invention further provides for the use of the liner of theinvention, preferably comprising calcium oxide, metallic calcium and/orcobalt chloride as getter material, for indicating the permeate contentof an adhesive covered with the liner. This indication is achievedthrough a change in the optical properties of the getter materialpresent in the liner. Thus, for example, calcium oxide changes colourfrom white to transparent as the binding of water progresses. Metalliccalcium as well loses its metallically opaque appearance and becomesincreasingly transparent. Therefore, as long as getter material canstill be recognized in the visual appearance of the unused state, thismay be taken to be an indication that there is as yet no diffusion, orat most low diffusion, of permeate to the adhesive that is to beprotected.

DRAWINGS

-   10: Carrier layer-   11: Release layer-   20-25: Layer of getter material

FIG. 1 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a continuous layer of getter material(20) in between.

FIG. 2 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a perforated layer of getter material(21) in between.

FIG. 3 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a perforated layer of getter material(22) in between, where the layer of getter material penetrates at leastpartly into the surface of the release layer and of the carrier layer.

FIG. 4 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a layer of particulate getter material(23) in between.

FIG. 5 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a layer of particulate getter material(23) in between, where the layer of getter material penetrates at leastpartly into the surface of the release layer and of the carrier layer.

FIG. 6 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a layer of particulate getter material(24) in between, in which the getter material is embedded in a matrixmaterial and comprises more than 50% by weight of the getter materiallayer.

FIG. 7 shows a liner of the invention consisting of a release layer (11)and a carrier layer (10) and also a layer of particulate getter material(25) in between, in which the getter material is embedded loosely in asheetlike textile structure material and comprises more than 50% byweight of the getter material layer.

EXAMPLES

Various liners provided with a getter material layer were produced. Theywere laminated to various adhesive tapes by means of a laboratory rolllaminator in a controlled-climate chamber at 23° C. and a relativeatmospheric humidity of 50%.

Adhesive Tapes

To produce adhesive tapes, different pressure-sensitive adhesives (PSAs)were applied, using a laboratory coating instrument, from a solution toa conventional liner which is not in accordance with the invention andis not impervious to permeation, this liner being of the type ALU I 38UV1 from Mondi, comprising an aluminium foil carrier, and dried. Thelayer thickness of the adhesive after drying was 25 μm in each case.Drying took place in each case at 120° C. for 30 minutes in a laboratorydrying cabinet.

K1: Pressure-sensitive Adhesive

100 parts Tuftec P 1500 SBBS with 30% by weight block polystyrenecontent from Asahi. The SBBS contains about 68% by weight diblockcontent. 100 parts Escorez 5600 hydrogenated HC resin with a softeningpoint of 100° C., from Exxon  25 parts Ondina 917 white oil comprisingparaffinic and naphthenic fractions, from Shell

The solvent used was a 2:1 mixture of toluene and acetone.

K2: Hotmelt Adhesive

100 parts Kraton FG 1924 maleic anhydride-modified SEBS with 13% byweight block polystyrene content, 36% by weight diblock and 1% by weightmaleic acid, from Kraton  25 parts Escorez 5600 hydrogenated HC resin(hydrocarbon resin) having a softening point of 100° C., from Exxon  1part aluminium acetylacetonate

The solvent used was a 2:1 mixture of toluene and acetone.

K3: Radiation-activatable Hotmelt Adhesive

25 parts Epiclon 835 LV bisphenol A and bisphenol F based epoxy resinfrom DIC, Japan, molecular weight M_(w) about 350 g/mol 25 parts Epicote1001 bisphenol based epoxy resin from Mitsubishi Chemical Company,Japan, molecular weight M_(w) about 900 g/mol 50 parts YP-70 bisphenol Aand bisphenol F based phenoxy resin from Nippon Steel Chemical Group,Japan, molecular weight M_(w) about 55 000 g/mol 1.5 parts  Irgacure 250iodonium salt-based UV photoinitiator from BASF (iodonium,(4-methylphenyl) [4-(2-methylpropyl) phenyl]-, hexafluorophosphate(1-))

The solvent used was methyl ethyl ketone.

K4: Heat-activatable Adhesive

90 parts Ultramid 1C copolyamide 6/66/136 from BASF, having a viscositynumber of 122 ml/g in 96% strength sulphuric acid in accordance with ISO307 10 parts EPR 166 bisphenol based epoxy resin from Bakelite, epoxidenumber of 184 20 parts PEG 2000 polyethylene glycol with an averagemolar mass of 2000 20 parts Foralyn 5040 tackifier resin from Eastman

The adhesive was prepared in a process as disclosed in DE102006047739A1, using ethanol as solvent.

The layers of adhesive were stored for 72 hours at 23° C. and 50%relative atmospheric humidity (atmosphere A). The water content of thelayers of adhesive was determined in each case before combination withthe liner.

Measurement of the Water Content

The water content was determined in accordance with DIN 53715(Karl-Fischer titration). Measurement took place on a Karl-FischerCoulometer 851 in conjunction with an oven sampler (oven temperature140° C.). A triple determination was carried out with an initial masseach time of around 0.3 g. The water content reported is the arithmeticmean of the measurements.

Water content [ppm] Layer of adhesive atmos. A K1 853 K2 551 K3 3216 K416400LinerCarrier Materials:

Carrier materials used for the liner were in one case a polyestercarrier approximately 75 μm thick (Lumirror 60.01/75 from TorayPlastics, hereinafter: PET) and also a polyester film approximately 30μm thick with an inorganic barrier layer coating (GX-P-F from ToppanPrinting, hereinafter: barrier-PET).

Also prepared was a polyolefin-based film (PO), by flat-filmcoextrusion. This film consisted of a 50 μm base layer and a 10 μm outerlayer. The base layer consisted of 91.3% (w/w) of polypropylene blockcopolymer Novolen 2309 L (BASF, melt index 6 g/10 min at 230° C. and2.16 kg, ethylene content about 6.5% (w/w)), 8.4% (w/w) of titaniumdioxide and 0.3% (w/w) of the HALS stabilizer Tinuvin 770.

The outer layer consisted of 85% of ethylene-multiblock copolymer InfuseD9107 (The Dow Chemical Company, d=0.866 g/cm3) and 15% of polyethyleneLD251 (ExxonMobil, d=0.9155). The outer layer material and also the baselayer was conveyed into the feed block of the coextrusion unit, withextrusion on an extrusion line from Dr. Collin.

Release Layers:

The outer layer of the abovementioned polyolefin film was also used asrelease layer (PO).

In the case of the silicone system used, the system in question is anaddition-crosslinking silicone system from Wacker. 9.75 g of DEH 915 (apolydimethylsiloxane functionalized with vinyl groups) were mixed with0.33 g of V24 (a methylhydrogenpolysiloxane) and 0.08 g of Kat OL (aplatinum catalyst, also known under the name “Karstedt catalyst”).Beforehand, both raw materials had been dried by means of zeolite beads(Molecular Sieves 4 Å from the supplier Sigma-Aldrich) at 23° C.

The release system was coated onto the carrier materials with a gettermaterial layer, with the aforementioned release system formulation beingapplied via a laboratory coating unit. The coating weight was 2 g/m².After coating, the release systems were crosslinked in a forced-air ovenat 160° C. for 30 seconds.

Getter Materials Used:

Identification Description Trade Name Supplier G1 calcium oxide calciumoxide Sigma-Aldrich nanopowder G2 lithium chloride lithium chlorideSigma-Aldrich anhydrous G3 calcium high-purity calcium Osnabrueggegranules G4 zeolite 3A Purmol 3 STH Zeochem

For application in thin layers, getter materials G2 and G4 were groundand screened where necessary so that there were no particles presentwhich were larger than the layer thickness. After the grindingoperation, these particles were regenerated by heat treatment in amanner known to the skilled person.

Production of the Liners:

The liners were produced in a glovebox under a nitrogen atmosphere at23° C. at 1 ppm water content.

Liners with the pulverulent getter materials G1, G2 and G4 were producedby scattering an amount of approximately 2 g/m² onto the outer layerside of the polyolefin-based carrier film, using a sieve.

Then a second polyolefin-based carrier film was laminated by the baselayer side onto the getter material layer by means of a heating press at160° C.

Alternatively the getter material was consolidated in the outer layer bymeans of a laboratory laminating instrument with silicone rolls at aroll temperature of 160° C. A layer of the silicone release system wasthen applied as described above onto the getter material layer.

For adhesive tapes with calcium as the getter material, the metal wasapplied by vapour deposition under reduced pressure onto the PET filmand onto the PET barrier film (in that case on the side bearing theinorganic barrier layer), producing in each case a getter material layerthickness of around 300 nm. Then a layer of the silicone release systemwas applied as described above onto the getter material layer.

Table 1 shows an overview of the liners produced which comprise layersof getter material:

TABLE 1 Getter material-filled liners Getter Carrier Getter materialamount Identification material layer [g/m²] Release layer L1 PET G3 0.47Silicone L2 Barrier PET G3 0.47 Silicone L3 PO G1 1 Silicone L4 PO G2 1Silicone L5 PO G4 1 Silicone L6 PO G1 1 PO L7 PO G2 1 PO L8 PO G4 1 POL9 PET — 0 Silicone (comparative example)

For further investigation, adhesive tape sections measuringapproximately 100×100 mm² were conditioned as already described aboveand immediately thereafter were lined with the liner at 23° C. and 50%relative atmospheric humidity, using a laboratory laminator with a rolltemperature of 80° C. The laminates produced in this way were storedunder the following atmospheres for 168 hours:

-   Atmosphere B: 23° C., sealed in vacuumized packaging impervious to    permeation-   Atmosphere C: 23° C., 95% relative atmospheric humidity

Lastly, the water content of the adhesive was determined in thespecimens. Here, samples were taken from the centre of the area of thespecimen, in order to avoid margin effects. The results are summarizedin Table 2:

TABLE 2 Determination of the water content Water content of adhesivesAssembly [ppm] storage after after Liner Adhesive atmosphereconditioning storage Example  1 L1 K1 atmos. B 853 309  2 L2 K1 atmos. B853 285  3 L3 K1 atmos. B 853 212  4 L4 K1 atmos. B 853 125  5 L5 K1atmos. B 853 388  6 L6 K1 atmos. B 853 259  7 L7 K1 atmos. B 853 186  8L8 K1 atmos. B 853 518  9 L1 K1 atmos. C 853 1180 10 L2 K1 atmos. C 853491 11 L3 K1 atmos. C 853 1220 12 L4 K1 atmos. C 853 852 13 L5 K1 atmos.C 853 1160 14 L6 K1 atmos. C 853 1190 15 L7 K1 atmos. C 853 817 16 L8 K1atmos. C 853 1290 17 L1 K2 atmos. B 551 208 18 L2 K2 atmos. B 551 133 19L3 K2 atmos. B 551 95 20 L6 K2 atmos. B 551 136 21 L1 K2 atmos. C 551803 22 L2 K2 atmos. C 551 263 23 L3 K2 atmos. C 551 806 24 L6 K2 atmos.C 551 785 25 L1 K3 atmos. B 3216 593 26 L2 K3 atmos. B 3216 459 27 L3 K3atmos. B 3216 310 28 L6 K3 atmos. B 3216 382 29 L1 K3 atmos. C 3216 520030 L2 K3 atmos. C 3216 641 31 L3 K3 atmos. C 3216 4650 32 L6 K3 atmos. C3216 4650 33 L1 K4 atmos. B 16400 3390 34 L2 K4 atmos. B 16400 2650 35L3 K4 atmos. B 16400 1770 36 L6 K4 atmos. B 16400 1690 37 L1 K4 atmos. C16400 34440 38 L2 K4 atmos. C 16400 5310 39 L3 K4 atmos. C 16400 3149040 L6 K4 atmos. C 16400 34800 Comparative examples C1 L9 K1 atmos. B 853965 C2 L9 K2 atmos. B 551 657 C3 L9 K3 atmos. B 3216 3840 C4 L9 K4atmos. B 16400 16940 C5 L9 K1 atmos. C 853 1337 C6 L9 K2 atmos. C 551894 C7 L9 K3 atmos. C 3216 6882 C8 L9 K4 atmos. C 16400 38700

The results show that liners of the invention are suitable for keepingpermeates away from adhesive tapes or for limiting the amount ofpermeate that penetrates (Examples 9-16, 21-24, 29-32 and 37-40 incomparison to the Comparative Examples C5-C8).

It is particularly advantageous for the liner to comprise a barrierlayer against one or more permeates or for the carrier material itselfto exhibit a strong barrier effect against the permeate (L2), since thenthe getter capacity is sufficient not only to scavenge the entire amountof the permeate to which it is exposed, but also, furthermore, to reducethe amount of permeate already present in the adhesive (Examples 10, 22,30, 38).

The surprisingly good suitability of the liners of the invention forremoving permeates from adhesive tapes is also shown by Examples 1-8,17-20, 25-28 and 33-36.

We claim:
 1. A release liner for the protection of adhesives, therelease liner comprising at least one abhesive release layer and atleast one layer of a getter material capable of sorbing at least onepermeable substance, wherein the getter material is at least onesubstance selected from the group consisting of lithium, beryllium,boron, sodium, magnesium, potassium, calcium, manganese, iron, nickel,zinc, gallium, germanium, cadmium, indium, caesium, barium, boron oxide,calcium oxide, chromium oxide, manganese oxide, iron oxide, copperoxide, silver oxide, indium oxide, barium oxide, lead oxide and mixturesof two or more of the above substances, wherein, when calcium isselected, the at least one substance of the getter material consists ofhigh-purity calcium granules.
 2. The release liner according to claim 1,further comprising at least one third layer that is a carrier layer. 3.The release liner according to claim 1, wherein the release linerconsists of a carrier layer, the abhesive release layer and the layer ofa getter material capable of sorbing at least one permeable substance.4. The release liner according to claim 1, further comprising a barrierlayer against one or more specific permeates.
 5. The release lineraccording to claim 1, wherein the getter material is at least onesubstance selected from the group consisting of magnesium, calcium,iron, barium, nickel, zinc, calcium oxide, chromium oxide, manganeseoxide, iron oxide, copper oxide, silver oxide, barium oxide and mixturesof two or more of the above substances, wherein, when calcium isselected, the at least one substance of the getter material consists ofhigh-purity calcium granules.
 6. The release liner according to claim 1,wherein the getter material is at least one substance selected from thegroup consisting of calcium, iron, barium, nickel, zinc, barium oxide,calcium oxide and mixtures of two or more of the above substances,wherein, when calcium is selected, the at least one substance of thegetter material consists of high-purity calcium granules.
 7. An adhesivecovered at least on one side and at least partially with the releaseliner according to claim
 1. 8. The adhesive according to claim 7,wherein the adhesive, before being contacted with the release liner, hasa permeate content of less than 1000 ppm.
 9. A method comprising:providing an adhesive tape that is at least partially covered on atleast one side with the release liner according to claim 1; andencapsulating optoelectronic components with the adhesive tape.
 10. Amethod comprising: providing the release liner according to claim 1; andat least partially covering an aerobically curing adhesive with therelease liner.
 11. A method comprising: providing the release lineraccording to claim 1; and at least partially covering a moisture-curingadhesive with the release liner.
 12. The release liner according toclaim 6, wherein, when calcium is selected, the high-purity calciumgranules consist of calcium.